1. Field of the Invention
The present invention relates to a gas supply path structure and a gas supply method adapted in such a way that a fluid path is formed for a compressible fluid (mainly, compressible gas) to flow into or out of the path and that the fluid is ejected from a predetermined portion midway of the fluid path and, particularly, this gas supply path structure is suitably applicable to a laser oscillating apparatus using it for supply of a laser gas, an exposure apparatus having the laser oscillating apparatus as a component, and a device production method therewith.
2. Related Background Art
In recent years so-called excimer lasers are drawing attention as high output lasers only which can be oscillated in the ultraviolet region, and they are expected to be applied in the electronics industries, chemical industries, energy industries, etc., specifically, to processing, chemical reaction, etc. of metal, resin, glass, ceramics, semiconductors, and so on.
The functional principles of excimer laser oscillating apparatus will be described. First, a laser gas of Ar, Kr, Ne, F2, He, Xe, Cl2, or the like filled in a laser tube is brought into an excited state by electron beam irradiation, discharge, or the like. In the case of the KrF excimer laser, for example, the excited F atoms are coupled with inactive Kr atoms being in the ground state to create KrF, which is molecules existing only in the excited state. These molecules are called excimers. The excimers are instable and soon emit ultraviolet light to fall into the ground state. This phenomenon is called spontaneous emission and the excimer laser oscillating apparatus is one making use thereof so as to amplify the emitted light into phase-aligned light in an optical resonator composed of a pair of reflectors and take it out in the form of a laser beam.
The excimer laser oscillating apparatus is becoming the mainstream of light sources used in various modern industries on one hand and has the problem of extremely short light emission time due to exhaustion of the laser gas with light emission on the other hand. Namely, particularly in the case of the KrF laser, the ArF laser, and the F2 laser among the excimer lasers, it is not easy to maintain the light emission over a long time, because a relatively long time is necessary for return from the state of light emission of the excited molecules to the original state of F2 molecules.
In order to extend the light emission time by replenishment with the laser gas, it is necessary to always supply the laser gas at high speed. Generation of gas flow at high speed, however, can result in forming a shock wave, which could cause incapability of functioning as a laser oscillating apparatus; specifically, it could cause an offset of the optical axis of laser, loosening of joints for the laser gas, breakage of ceramics, metal fatigue, and so on. For example, when exposure or the like is carried out, vibration caused by the shock wave will be fatal disturbance rather than the above.
The present invention has been accomplished in view of the above problem and an object of the present invention is to provide a gas supply path structure (and a gas supply method) that can suppress occurrence of the shock wave while forming the gas flow at high speed close to the speed of sound in simple structure. A further object of the present invention is to provide a laser oscillating apparatus with long emission time equipped with the gas supply path structure, an exposure apparatus with high performance equipped with the laser oscillating apparatus, and a method for producing a high-quality device by use of the exposure apparatus.
A compressible fluid supply path structure according to the present invention is a compressible fluid supply path structure, said compressible fluid supply path structure being of a convergent-divergent nozzle type, said compressible fluid supply path structure comprising:
a fluid inlet into which a compressible fluid is made to flow;
a throat portion for controlling said compressible fluid to a speed less than a speed of sound;
a fluid outlet of which said compressible fluid is made to flow out; and
a circulation system for circulating said compressible fluid flowing out of said fluid outlet into said fluid inlet.
The compressible fluid supply path structure may be constructed in either one of the following configurations:
a ratio of a pressure at said fluid inlet to a pressure at said fluid outlet is not less than a ratio of critical pressures;
the compressible fluid supply path structure is shaped so as to decrease disturbance caused by said compressible fluid;
the compressible fluid supply path structure is a structure without an inflection point;
the compressible fluid supply path structure further comprises at least one pressure correcting means for correcting a pressure at said fluid inlet or at said fluid outlet;
the correction for the pressure by said pressure correcting means is carried out near said fluid inlet;
the compressible fluid supply path structure further comprises at least one temperature correcting means for correcting a temperature at said fluid inlet or at said fluid outlet;
said temperature correcting means has a cooling function and said cooling is effected near said fluid outlet;
the compressible fluid supply path structure further comprises vertical width adjusting means for adjusting a vertical width of said throat portion;
the compressible fluid supply path structure is symmetric with respect to said throat portion at the center.
Another compressible fluid supply path structure according to the present invention is a compressible fluid supply path structure comprising:
a fluid inlet into which a compressible fluid is made to flow;
a predetermined portion for controlling said compressible fluid to a speed less than a speed of sound;
a fluid outlet of which said compressible fluid is made to flow out;
at least one temperature correcting means for correcting a temperature at said fluid inlet or at said fluid outlet; and
a circulation system for circulating said compressible fluid flowing out of said fluid outlet into said fluid inlet.
The above compressible fluid supply path structure may be constructed so that said temperature correcting means has a cooling function and so that said cooling is effected near said fluid outlet.
A compressible fluid supply method according to the present invention is a compressible fluid supply method comprising:
a step of making a compressible fluid flow into a fluid inlet of a compressible fluid supply path structure of a convergent-divergent nozzle type;
a step of controlling said compressible fluid to a speed less than a speed of sound, at a throat portion of said compressible fluid supply path structure;
a step of making said compressible fluid flow out of a fluid outlet of said compressible fluid supply path structure; and
a circulation step of circulating said compressible fluid flowing out of said fluid outlet, into said fluid inlet by a circulation system.
In the above compressible fluid supply method, said compressible fluid supply path structure may be arranged so that a ratio of a pressure at said fluid inlet to a pressure at said fluid outlet is not less than a ratio of critical pressures.
Another compressible fluid supply method according to the present invention is a compressible fluid supply method comprising:
a step of making a compressible fluid flow into a fluid inlet of a compressible fluid supply path structure;
a step of controlling said compressible fluid to a speed less than a speed of sound, at a predetermined portion of said compressible fluid supply path structure;
a step of making said compressible fluid flow out of a fluid outlet of said compressible fluid supply path structure;
a step of correcting at least one of temperatures at said fluid inlet and at said fluid outlet by temperature correcting means of said compressible fluid supply path structure; and
a circulation step of circulating said compressible fluid flowing out of said fluid outlet, into said fluid inlet by a circulation system.
In the above compressible fluid supply method, said temperature correcting means may have a cooling function and said cooling may be effected near said fluid outlet.
A laser oscillating apparatus according to the present invention is a laser oscillating apparatus comprising:
a gas supply path structure for supplying a laser gas, said gas supply path structure being of a convergent-divergent nozzle type,
said gas supply path structure comprising:
a fluid inlet into which said laser gas is made to flow;
a throat portion for controlling said laser gas to a speed less than a speed of sound; and
a fluid outlet of which said laser gas is made to flow out.
The laser oscillating apparatus may be constructed in either one of the following configurations:
said gas supply path structure further comprises a circulation system for circulating said laser gas flowing out of said fluid outlet, into said fluid inlet;
said gas supply path structure is arranged so that a ratio of a pressure at said fluid inlet to a pressure at said fluid outlet is not less than a ratio of critical pressures;
said laser gas is an excimer laser gas which is a mixture of F2 gas with at least one inert gas selected from Kr, Ar, Ne, and He;
said gas supply path structure is a structure without an inflection point;
said gas supply path structure further comprises at least one pressure correcting means for correcting a pressure at said fluid inlet or at said fluid outlet;
said gas supply path structure further comprises at least one temperature correcting means for correcting a temperature at said fluid inlet or at said fluid outlet;
said temperature correcting means has a cooling function and said cooling is effected near said fluid outlet;
said gas supply path structure further comprises vertical width adjusting means for adjusting a vertical width of said throat portion;
said circulation system is comprised of at least one bellows pump;
said circulation system is comprised of at least one circulating pump;
said circulation system is comprised of at least one blower;
said circulation system is comprised of at least one Sirocco fan.
Another laser oscillating apparatus according to the present invention is a laser oscillating apparatus comprising:
a gas supply path structure group for supplying a laser gas, said gas supply path structure group being of a shape of gas supply path structures of a convergent-divergent nozzle type connected in series,
said gas supply path structure group comprising:
a fluid inlet into which said laser gas is made to flow;
a central part for controlling said laser gas to a speed greater than a speed of sound; and
a fluid outlet of which said laser gas is made to flow out.
The above laser oscillating apparatus may be constructed in either one of the following configurations:
said gas supply path structure group further comprises a circulation system for circulating said laser gas flowing out of said fluid outlet, into said fluid inlet;
said laser gas is an excimer laser gas which is a mixture of F2 gas with at least one inert gas selected from Kr, Ar, Ne, and He;
said gas supply path structure group is a structure without an inflection point;
said gas supply path structure group further comprises at least one pressure correcting means for correcting a pressure at said fluid inlet or at said fluid outlet
said gas supply path structure group further comprises at least one temperature correcting means for correcting a temperature at said fluid inlet or at said fluid outlet;
said gas supply path structure group further comprises vertical width adjusting means for adjusting a vertical width of said central portion;
said circulation system is comprised of at least one bellows pump;
said circulation system is comprised of at least one circulating pump;
said circulation system is comprised of at least one blower;
said circulation system is comprised of at least one Sirocco fan.
An exposure apparatus according to the present invention is an exposure apparatus comprising:
a laser oscillating apparatus, said laser oscillating apparatus generating illumination light,
said laser oscillating apparatus comprising a gas supply path structure for supplying a laser gas, said gas supply path structure being of a convergent-divergent nozzle type,
said gas supply path structure comprising:
a fluid inlet into which said laser gas is made to flow;
a throat portion for controlling said laser gas to a speed less than a speed of sound; and
a fluid outlet of which said laser gas is made to flow out,
a first optical system for radiating said illumination light from said laser oscillating apparatus onto a reticle in which a predetermined pattern is formed; and
a second optical system for radiating said illumination light having passed through said reticle, onto a surface to be irradiated.
Another exposure apparatus according to the present invention is an exposure apparatus comprising:
a laser oscillating apparatus, said laser oscillating apparatus generating illumination light,
said laser oscillating apparatus comprising a gas supply path structure group for supplying a laser gas, said gas supply path structure group being of a shape comprised of gas supply path structures of a convergent-divergent nozzle type connected in series,
said gas supply path structure group comprising:
a fluid inlet into which said laser gas is made to flow;
a central part for controlling said laser gas to a speed greater than a sound speed; and
a fluid outlet of which said laser gas is made to flow out,
a first optical system for radiating said illumination light from said laser oscillating apparatus onto a reticle in which a predetermined pattern is formed; and
a second optical system for radiating said illumination light having passed through said reticle, onto a surface to be irradiated.
A device production method according to the present invention is a method for producing a device, said method comprising:
a step of coating a surface to be irradiated, with a photosensitive material;
a step of effecting exposure of a predetermined pattern in said surface to be irradiated, coated with said photosensitive material, using the exposure apparatus as stated above; and
a step of developing said photosensitive material on said surface after the exposure.
The above device production method may be arranged so that said surface to be irradiated is a wafer surface and so that a semiconductor element is formed on said wafer surface.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.